PHP include(): File size & performance

Question

An inexperienced PHP question:

I've got a PHP script file that I need to include on different pages lots of times in lots of places.

I have the option of either breaking the included file down into several smaller files and include these on a as-needed basis... OR ... I could just keep it all together in a single PHP file.

I'm wondering if there's any performance impact of using a larger vs. smaller file for include() in this context? For example, is there any performance difference between a 200KB file and a 20KB file?

Thank you.

Answer 1

There will be a difference, between a 200KB and a 20KB file... But you will probably not notice it : a 200KB file is not that big -- and you generally use a lot of files that are not "small", when you're building a big application.

There are two things that take time, when you're loading a .php file :

• The PHP source code is "compiled" to "opcodes" -- that's quite equivalent to JAVA bytecode
  • This is done each time a PHP file is included, by default
  • But, using some opcode cache like APC, those opcodes can be kept in memory, and this compilation stuff not done each time anymore -- which is great : it'll mean less CPU used, as the compilation will not be done anymore (it'll be done only once in a while).
• The opcodes are executed
  • Depending on what you script contains, this can take some time, or not :
  • If the file only contain functions or classes definitions, this will not take much time : nothing will get executed.
  • If the file contains instructions, it'll take more time ^^

As a sidnote : in a general situation, you'll gain a lot more time/cpu/resources optimizing your SQL queries, or adding some caching mecanism, than thinking about that kind of stuff.